Exchange Flashcards
What substances must be exchanged with the environment in an organism?
Heat
Respiratory gases
Excretory products
Nutrients
What factors affect the rate of exchange?
Length of diffusion pathway Surface area Concentration and pressure gradient Carrier proteins Temperature
What are the methods of exchange?
Active, bulk and Co transport
Osmosis
Simple facilitated diffusion
How do you calculate the volume and surface area of a sphere?
SA=4x3.124xr^2
Volume= 4/3x3.142xr^3
Why is sa:vol smaller in large animals?
As size increases volume increases faster than sa
Why do mammals require a specialised exchange surface and transport system?
Small sa:vol
Not enough can diffuse in and out to supply volume
Large diffusion gradient= can’t reach cell quick enough
What are the adaptions of a specialised exchange surface? Give examples
Layer of cells one cell thick
Movement of internal and external mediums
Large sa:vol
Selectively permeable membrane
What is the advantage of having a large surface area?
More carrier and channel proteins
More places to diffuse across
What is the disadvantage of having a thin surface membrane?
How is this overcome?
Easily damaged and dehydrated
Inside organism
Why do mice have a high metabolic rate?
Move lots more
Large sa:vol
Heat lost easily
Constantly replaced by energy released via Respiration
High rate of Respiration
Why do single celled organisms not need a circulatory system?
Short diffusion pathway meaning substance can be supplied quick enough
Why do single celled organisms have a high rate of exchange?
Large sa:vol
Short diffusion pathway
How are the tracheas in humans and insects similar?
Humans = cartilage
Insects= chitin
Rings
What is a spiracle and how is it adapted?
Pore in side of insects
Hairs and ability to close to conserve water
Why are insects limited to the size they can grow to?
Must remain small to retain short diffusion pathway
How are Respiratory gases moved in an insect?
Mass tansport: Abdominal pumping
Drawn in (lactate produced lowering wp so water drawn into muscle cells so last part= gas phase)
Diffusion down partial pressure gradient
Describe the structure of the gills
Gill arches
Gill filaments
Gill lamella
What is the operculum ?
Hard bony flap that deoxygenated water leaves out of
How are the gills adapted?
Thin surface (one cell thick)
Movement of external and external mediums
Good blood supply
Large sa
Why might fish die in warm water?
Oxygen is less soluble in warm water (already not very soluble)
Why do fish require specialised gas exchange surfaces?
Small sa:vol
Waterpriof and gas tight outer coating
Oxygen not very soluble in water
What best describes this mechanism: blood flows one way as water flow in the opposite direction?
Countercurrent exchange principle
Why is the countercurrent exchange principle important?
Prevents equilibrium being reached
Diffusion across whole length of gill
Blood always next to wtae reith higher oxygen concentration
What is the opposite to countercurrent flow?
Parallel flow
During the day what is the net movement of co2 and o2 in a leaf? Why?
Co2 in o2 out
Rate of Photosynthesis exceeds respiration
During the night what is the net movement of co2 and o2 in a leaf? Why
O2 in co2 out
Photosynthesis doesn’t occur at night
What occurs at dawn and dusk?
Compensation point as rate of Photosynthesis and Respiration are equal
No net diffusion
How do guard cells open and close the stomata?
Make sugar
Lower wp
Water moves in
Makes turgid as thick inflexible inner wall creates opening
What is different about guard cells?
Have thick and inflexible inner wall
Have chloroplasts to make sugar to lower wp
What state are guard cells in when the stomata is closed?
Plasmolysis
Why do plants not have ventilation or ma’s transport system?
Have thin diffusion pathway so can diffuse
Ventilation would cause too much water loss
Adaptions of leaf for gas exchange
Flat and thin (large sa and short diffusion pathway)
Air spaces in mesophyll= large sa and diffusion in gas phase so quicker
How do insects limit water loss?
Hairs around spiracles trap moist air
Waterproof cuticle over chitin exoskeleton
Spiracles can close
Small sa:vol = minimise área over which water lost
How do plants limit water loss?
Close stomata
Waxy cuticle
How do xerphytic plants reduce water loss?
Reduce sa = circular cross section
Curl leaves, hairs around stomata, sunken stomata= trap moist air
Thick Waxy cuticle
Why might having needle shaped leaves be contravertial for plants?
Smaller sa:vol
Less gas exchange
What is a xerphytic plant?
Plant adapted to live in areas of short water supply
Give examples of xerphytic conditions
Salt marshes= hard to obtain water
High wind speeds= high conc gradient
Sand dunes= water drains away
Very cold= water trapped in ice
Why are large volumes of gases exchanged in large organisms?
High body temp= high metabolic rate= more respirtion
Many cells to supply
What structure does air pass to get to the lungs?
Nasal cavity Epiglottis Larynx Trachea Bronchus Bronchioles Alveoli
Why are the lungs inside the body?
The prevent dehydration and damage due to thin layer of one cell
What are the lungs?
Two lobed structures
Describe the structure or the trachea
C shaped ring of cartilage =prevent collapse
Thick Smooth muscle
elastic fibers
Ciliated epithelial cells=waft mucus up
Goblet cells= produce mucus
Describe the structure of the Bronchus
Small sections of cartilage
Ciliated epithelial cells
Goblet cells
Smooth muscles
Glands
Describe the changing structure of the Bronchioles as you go towards the alveoli
More smooth muscle less/no cartilage
Contact to regulate ventilation
Made of epithelial cells
Describe the structure of a alveoli bundle
Alveoli with tissue fluid, collagen and elastic fibres between them
Network of capillaries
Describe the structure of a alveoli and their function
Squamous epithelial cells= reduced diffusion pathway
Water= because cell membranes are permeable
Elastic fibres allow recoiling
Describe how the capillaries near the alveoli are adapted for gas exchange
Squamous endothelial cells=short diffusion pathway
Red blood cells compressed up to walls
Blood is slowed
Why might alveoli seem to be different sizes when looked at through a microscope?
Cut in different planes
How are the lungs adapted for gas exchange?
Short diffusion pathway:
Squamous endo and epithelial cells
Compressed erythrocytes
Maintain conc gradient:
Elastic fibres= recoil
Flow of blood
Ventilation
Large sa:
Alveoli and pulmonary capillary walls
Flow of blood slows= more time to diffuse
Alveoli packed closely together
Why do people with asthma struggle to breath?
Muscles in Bronchus and Bronchioles contract reducing diameter of lumen
Goblet cells produce excess thick mucus
Reduced air flow
What is emphysema?
When the walls of alveoli break down and fuse
Large alveoli of reduced number = smaller sa:vol
Thick walls = long diffusion pathway
Elastin not replaced
What is fibrosis and why does it cause breathing difficulties?
Elastic fibres in lungs become stiff
Reduce volume of lungs (can’t strech)
What are the risk factor for lung disease?
Genetic makeup
Smoking
Infection
Occupation
Air pollution
Describe inhalation
External intercostal muscles contract, internal relax
Diaphragm contracts and flattens from dome shape
Sternum and runs move up and out
Elastic fibres strech
Volume in lungs increases
pressure in lungs decreases below atmospheric pressure
Air moves in down pressure gradient
When does the cartilage in the trachea provide its function?
During inspiration and pressure drops
Define inhalation
Pressure in lungs decreases below atmospheric pressure and air moves into lungs
Define exhalation
Pressure in lungs increases above atmospheric pressure air is forced out of lungs
Describe exhalation
Internal intercostal muscles contract (only during exercise ) and external relax
Elastic fibres of lungs recoil
Diaphragm relaxes and returns to dome shape
Sternum and ribs move in and down
Volume of lungs decreases and pressure increases above atmospheric pressure
Air is expelled
Is inspiration active?
Yes because external intercostal muscles contract
Is expiration active?
No passive when at rest as elastic fibres recoil
What is the equation for pulmonary ventilation?
Pulmonary ventillation=
Tidal volume X breathing rate
Define and give units for pulmonary ventilation
Volume of air moved into lungs in a minute
Dm^3min^-1
Define and give units for tidal volume
Maximum volume of air inspired after maximum exhalation at rest
Dm^3
Define and give units for breathing rate
Breaths per min
Breathsmin^-1
How does reducing stomata diameter help plants survive?
Less water lost
More water available for Photosynthesis
